Process for production of soy-containing breakfast cereals

ABSTRACT

Process for making ready-to-eat breakfast cereal containing soy protein. Soy protein is made more palatable by subjecting it to a partial hydrolysis reaction in the presence of a specific mixture of proteolytic enzymes. A mixture of proteolytic enzyme papain and at least one other proteolytic enzyme has the effect of more efficiently causing the partial hydrolysis of soy protein than does a single enzyme at the same addition level.

United States Patent Bedenk et a1.

PROCESS FOR PRODUCTION OF SOY-CONTAINING BREAKFAST CEREALS Inventors:William T. Bedenk, Springfield Twp., Hamilton County; David E. OConnor,Cincinnati, both of Ohio The Proctor & Gamble Company, Cincinnati, OhioFiled: Oct. 5, 1970 Appl. No.: 78,274

Assignee:

[1.8. CI 99/81, 99/83, 99/17 Int. Cl A231 1/18 Field of Search 99/14,17, 81, 82,

References Cited UNITED STATES PATENTS 2/1948 Lulce 99/83 PrimaryExaminerRaymond N. .Jones Attorney-Richard C. Witte [5 7] ABSTRACTProcess for making ready-to-eat breakfast cereal containing soy protein.Soy protein is made more palatable by subjecting it to a partialhydrolysis reaction in the presence of a specific mixture of proteolyticenzymes. A mixture of proteolytic enzyme papain and at least one otherproteolytic enzyme has the effect of more efficiently causing thepartial hydrolysis of soy protein than does a single enzyme at the sameaddition level.

16 Claims, No Drawings PROCESS FOR PRODUCTION OF SOY-CONTAININGBREAKFAST CEREALS BACKGROUND OF THE INVENTION This invention relates tobreakfast cereals of the ready-to-eat or cold cereal class, the twoterms used herein interchangeably. By the process herein describedcereal products are produced that are highly nutritional and haveexcellent eating qualities.

Cereal manufacturers have long tried to incorporate a significant amountof soy protein into a cold cereal product but until recently have beenunsuccessful. A cold cereal product containing soy protein is desirablebecause of the enhancement of the nutritional value of the cerealresulting from the soy protein. However, the soybean has certaindeficiencies that have delayed their use in cereal products intended forhuman use. For instance, the soybean possesses a rather unacceptabletaste so that at only relatively low levels of soybean content is thecharacteristic soy taste undetectable. Various debittering techniqueshave been developed to remove the organoleptically objectionablecomponents of the soybean and have met with some success. Sugar coatingsand various flavor additives also have been used to mask the bitter soyflavor.

Other drawbacks experienced with the soybean as a cold cereal componenthave been its adverse effect on the cereals eating quality and also theeffect it has on the processability of the ingredients into a formsuitable for human consumption. Eating quality refers to a cold cerealscrispness retention and tenderness. Crispness retention is thecharacteristic of a cold cereal product after having been wetted by anaqueous liquid, e.g., milk that involves the retention of a solidcrunchy structure that is detected during eating. Crispness of a cerealsteadily decreases after being wetted until eventually a soggy productis the result. Tenderness, on the other hand, refers to the ease withwhich the cereal particle breaks down in the mouth. A cereal product canbe deficient in this respect by being either too hard or too tough. As ageneral rule a cereal product becomes more tender when soaked in anaqueous liquid with the passing of time. Soy containing cereal productsare undesirable because the soy diminishes the cold'cereal productscrispness retention and also because the soy imparts a toughness orleatheryness to the cereal when soaked in liquid.

Still another drawback experienced with the use of soy in a breakfastcereal encountered in puffed" products is the adverse effect soy exertson the puffability of a cereal particle. Ready-to-eat breakfast cerealsare produced in many forms and shapes such as flakes, puffed cerealpieces, biscuits, granules, shreds and the like. A part of the processof producing the flake and puffed form involves what is referred to as apuffing operation. During puffing, relatively dense flakes and particlesare converted into lighter, more porous flakes and particles by causingtrapped moisture to expand very rapidly from the liquid state to thevapor phase. Soy, however, hinders this change in structure and therebyindirectly affects also the eating quality of the cereal sincewell-puffed cereals are more crisp and tender than poorly puffedcereals.

Commonly assigned, copending applications Ser. No. 50,980, Production ofReady-to-Eat Breakfast Cereals Containing Soy Flour by Alexander LLiepa, Ser. No. 50,925, High Protein Ready-to-eat Breakfast CerealsContaining Soy Concentrate by William T. Bedenk, and

Ser. No. 50,924, High Protein Ready-to-Eat Breakfastv Cereals ContainingSoy Isolate by William T. Bedenk, all contain disclosures as to thetreatment of their re spective soy protein sources to make them morecompatible. The treatment comprises mixing 50 to percent water by weightof the total mixture with the protein source and adding 25 ppm 2500 ppmof a proteolytic enzyme or enzymes based on the soy protein source. Thismixture is held at 80F to 160F for l minute to minutes to cause apartial hydrolysis of the soy protein source. Such a treatmentunexpectedly improves the flavor, crispness retention, tenderness, andpuffability of a cereal product containing the soy protein to such anextent that the soy protein can form a major portion of the end product.

In accord with this invention a cold cereal product is producedcontaining a soy protein source which has been partially hydrolyzed in amore efficient manner than known heretofore. The total proteolyticenzyme level needed to obtain a partial hydrolysis to the degree desiredis reduced to a level which prior to this invention was ineffective.

It is the general object of this invention to produce a high proteincontent ready-to-eat cereal.

It is a further object of this invention to produce a soyprotein-containing high protein content ready-to-eat breakfast cereal bya process whereby the soy. protein is partially hydrolyzed to the degreedesired in a very efficient manner.

It is a further object of this invention to produce a soyprotein-containing high protein content ready-to-eat breakfast cereal bya process whereby the soy protein is partially hydrolyzed in thepresence of a specific mixture of proteolytic enzymes, which specificmixture causes a more efficient partial hydrolysis than does a singleenzyme at the same addition level.

More specifically, it is an object of the present invention to produce ahigh protein content ready-to-eat cereal by a process wherein theprotein source is partially hydrolyzed in the presence of papain and atleast one other proteolytic enzyme. i

This and other objects will become apparent from the followingdescription of the invention.

SUMMARY OF THE INVENTION Briefly stated, this invention concerns theproduction of highly palatable and nutritive beakfast cereal products.More specifically, the cold cereal products of this invention comprise asoy protein source and a cooked cereal grain in proportions such thatthe total protein content of the breakfast cereal is at least 20percent. Such a product is produced by mixing water with a soy proteinsource, papain and at least one other proteolytic enzyme. The abovemixture is then exposed to an elevated temperature for a length of timesufficient to cause a partial hydrolysis of the soy protein source andthen further processed into the desired end product.

DESCRIPTION OF THE INVENTION scription to follow. All three proteinsources are commercially available and the use of them in the presentinvention can be done interchangeably. Any deviations in the processingof the three protein sources will be noted in the description to follow.The soy protein sources useful in this invention are defatted andrefined soybeans. Soy flour contains 40 up to 70 percent protein, soyprotein concentrate contains 70 up to 90 percent protein and soy proteinisolate contains 90 up to 100 percent protein.

In accord with this invention soy protein is made more palatable bysubjecting it to a partial hydrolysis. The partial hydrolysis isaccomplished by including in the reaction mixture the proteolytic enzymepapain plus at least one other proteolytic enzyme. The mixture of theabove enzymes is able to promote a partial hydrolysis while an equalamount of a single enzyme does not cause a partial hydrolysis to thesame degree. The degree of partial hydrolysis of the soy protein isimportant because it has a direct effect on the soy-containing endproducts taste. That is, a different degree of partial hydrolysis in twoprotein sources will result in different eating qualities of two cerealproducts containing the respective soy protein source. The greater thedegree of partial hydrolysis of the soy protein source the more tenderwill be a cold cereal product containing that partially hydrolyzed soyprotein and, hence, more desirable up to a point, i.e., a too tenderproduct is also undesirable to the average consumer. As taught herein,the exact degree of partial hydrolysis desired is obtained in a veryefficient manner when the soy protein and water are reacted in thepresence of papain and at least one other proteolytic enzyme at theconditions set out hereinafter. The reaction is efiicient in the sense alower total proteolytic enzyme level promotes the partial hydrolysis tothe exact degree desired when the specific enzume mixture papain and atlease one other proteolytic enzyme is included in the reaction mixtureas opposed to other enzyme mixtures or single enzymes at the samereaction conditions.

After the proper degree of partial hydrolysis of the soy protein sourcehas occurred, it is further processed into the final product. Apreferred method comprises extruding the partially hydrolyzed soyprotein source into strands of a relatively small cross-sectional area,pelletizing the strands, flaking and puffing or immediately puffingafter pelletizing. Additional steps such as toasting or coating can beadded to further enhance the product's taste and/or appearance.

In a preferred embodiment of this invention a gelatinized cereal grainis added to a partially hydrolyzed soy protein in proportions such thatthe total protein content of the end product is at least percent. Thismixture is further processed into a final form suitable for humanconsumption in the manner above described for the soy source alone.

By the process of the present invention the soy protein is made morepalatable by forming a mixture of the soy protein source, water, theproteolytic enzyme papain, and at least one other proteolytic enzyme.Quite unexpectedly, the above specific mixture of proteolytic enymespromotes a partial hydrolysis to the degree desired while an equal levelof either papain alone, another proteolytic enzyme or a mixture of otherproteolytic enzymes under the same reaction conditions does not resultin the same degree of partial hydrolysis. Only at levels of proteolyticenzymes substantially greater than the total level of papain and atleast one other proteolytic enzyme is there obtained the same degree ofpartial hydrolysis under the same conditions. In that proteolyticenzymes are relatively expensive it it imperative that as low a level ofproteolytic enzyme as possible commensurate with the proper degree ofpartial hydrolysis be used.

No hydrolysis of the soy protein or only a partial hydrolysis less thanthat achieved by following the reaction conditions of this inventiongives an unacceptable tasting product as well as a poorly processableingredient. A degree of hydrolysis of the soy protein in excess of thatexperienced under the conditions set out hereinafter results in aproduct having an unacceptable taste. Only when the soy protein ispartially hydrolyzed to the degree taught herein and further processedto an end product is there obtained an acceptable soy-containing highprotein ready-to-eat breakfast cereal.

The proteolytic enzymes useful in the present invention in conjunctionwith papain are selected from any of several known proteolytic enzymesor mixtures thereof extracted from animal, plant, fungal, or microbialsources. A primary consideration in the enzyme or enzyme mixture used isthat it must not contribute a significantly objectionable flavor or odorto the final product. Some examples of proteolytic enzymes foundeffective in the soy protein partial hydrolysis step that can be usedwith the papain are pepsin, bromelin, ficin, alcalase, maxitase,therrnoase, pronase, and mixtures thereof.

In this invention, 15 ppm 2500 ppm of papain and 5 ppm-2,500 ppm of atleast one other proteolytic enzyme by weight of the soy protein issufficient to cause the desired degree of partial hydrolysis when thereaction mixture is exposed to a temperature of F to 160F for 1 minuteto 120 minutes. The preferred levels of enzymes are ppm 300 ppm of thepapain and 100 ppm 300 ppm of at least one other proteolytic enzymebased on the weight of the protein. Temperatures of F to F and times of1 minute to 5 minutes are preferred.

The amount of water needed for the partial hydrolysis reaction isbasically determined by apparatus limitations. That is, the lower limitof water is determined by the capability of the mixing equipment. Thelower the level of water the more viscous will be the resultant mixture.On the other hand, an excessive amount of water in the partialhydrolysis reaction would necessitate additional work in reducing thewater level in subsequent processing steps. The preferred level of wateris 50 to 80 percent based on the total weight of the mixture. The mostpreferred level is 55 to 60 percent based on the total weight of themixture.

Under the above conditions the soy protein source is partiallyhydrolyzed to the extent that a cold cereal product containing the soyprotein is acceptable with regard to taste, tenderness, crispnessretention, and processability.

An equal level of a single enzyme, e.g., papain or any other enzyme, andthe same reaction conditions produces an end product which is not asacceptable with regard to eating quality and processability as theproduct produced in accord with this invention, thereby indicating thatthe soy protein source has not been partially hydrolyzed to the degreeneeded. That such an effect would be obtained with the specific mixtureof proteolytic enzymes, papain and another enzyme as opposed to singleenzymes or any other mixture was quite unexpected.

The production of a cold breakfast cereal containing the partiallyhydrolyzed soy protein is done by various general procedures used formaking cold cereal products and depends in large part on the desiredform, type, or condition of the final product. Typically the partiallyhydrolyzed soy protein is extruded into strands of a relatively smallcross-sectional area and thereafter sliced into small lengths therebyforming small pelletlike particles. These pellet-like particles arepartially dried, if necessary, and formed into flakes. The flakes arethen subjected to a puffing operation to transform them into less dense,more porous, and tender flakes. Toasting and/or a coating operation maybe employed to enhance the color and/or flavor of the resultant proteinfortified cereal product. Alternatively, instead of producing aflake-like product, the flaking step can be omitted with a puffedpellet-shaped product being the result.

In the preferred method of transforming the partially hydrolyzed soyprotein-water dough into the finished product, the first step is toextrude the dough into strands. An extruder has the effect of mixing theingredients even more intimately and of forming the dough into a shapeeasier to handle and more adaptable for existing equipment. Relativelylow pressures in the extruder are sufficient for this operation.Pressures within the range of 500 p.s.i.g. to L000 p.s.i.g. arepreferred. Lower pressures can be used but should preferably be avoidedsince less of a mixing action in the extruder results from the lowcompressive forces associated with low pressures. Pressures higher than1,000 p.s.i.g. exert little extra benefits and for this reason areavoided. Temperatures employed in the extrusion process are not acritical feature but do have some effect on the handling characteristicsof the extrudant, such as stickiness and body. Temperatures fallingwithin the range of 140F to 200F have been found to be satisfactory.

The shape of the strands that issue from the extruder is determined bythe particular extruder die used in the outlet of the extruder and thesestrands, in turn, greatly influence the shape of the individualparticles of the final product. For instance, if the shape of the strandis circular in its cross-sectional area the ready-to-eat cereal madefrom this strand will have a different shape or configuration than willa cereal product made from strands that are square, triangular, or anyother shape in its cross-sectional area. The particular die used in theextruder is a matter of choice dictated primarily by the shape desiredfor the final product.

The strands that are extruded from the extruder are next sliced to formpellet-like particles. The choice of the crosssectional size of thestrand issuing from the die and length of cut depends on the sizerequirement of the final individual pieces of cereal. Such parametersare easily determined.

After pelletizing, the pellet-like particles are tempered, if necessary,and run through flaking rolls. Depending on the formulation and processconditions used throughout the process, it may be necessary to allow thestrands and freshly cut pellets to cool down and/or dry somewhat. Thistempering has the effect of reducing the tackiness oftentimes associatedwith partially processed cereal dough. A hold time of up to 30 minutesis sufficient to temper the strands while a hold time of up to 2 minutesis sufficient for the freshly cut pellets. With some formulations theremay be no sticking problem in which case the strands and/or pellets canpass directly to the next operation without any tempering step.

If a flake-type cereal product is desired, the next step afterpelletizing is mechanically modifying the pellets to a flake form. Thiscan be accomplished by passing the pellets between a pair of cooperatingrollers or a roller and a flat surface spaced apart a distancesufficient to produce the desired flake thickness. In accord with thisinvention it has been found that a flake thickness of 7 to 12 mils issufficient to produce a satisfactory product. As the flakes leave therolls they are in a dense and relatively hard condition. Such a flake isunacceptable to the average consumer and, accordingly, an additionalprocessing step must be performed to produce a lighter and more porousflake structure.

Breakfast cereals obtain the desired flake structure by a process knownas puffing. Puffing of the flake is also quite important in that itenhances the flakes crispness and tenderness. Cereal flakes containinguntreated soy protein are difficult to puff but, unexpectedly, soyprotein when partially hydrolyzed in the manner heretofore describeddoes not act as a hindrance on puffing but rather actually improvespuffability. This factor is of importance in that the more porous typeflakes have a tendency to be more tender than the less porous or lesspuffed flake. Additionally, soy flavor is diminished even more in thebetter puffed of two soycontaining flakes. Basically a cereal is puffedby causing trapped moisture in the flake to expand very rapidly from theliquid state to the vapor phase. Rapid heating or a rapid decrease inthe pressure are the methods commonly used to convert dense hard flakesinto the more palatable porous tender flake. Both methods are well knownand are commonly used throughout the industry. Gun puffing is an exampleof the principle of a rapid decrease in pressure. In this process thecereal flakes are first heated under high pressure and then the pressureis rapidly released to achieve the puffing ef feet. The processdisclosed in U.S. Pat. No. 3,253,533 is an example of a rapid heatingpuffing method. Commonly assigned copending application Ser. No. 76771,Apparatus and Process of Pujfing, byWilliam T. Bedenk and LawrenceGrabel, also discloses a rapid .heating puffing method.

To achieve the optimum puffing, care must be taken in controlling theinitial moisture content of the unputfed flake. The specific moisturecontent that is best depends on the particular puffing; process utilizedand the particular grain in admixture with the soy isolate. Forinstance, for a blend of soy isolate and cooked gelatinized com amoisture content of 12 to 14 percent is optimum for gun puffing while10-] 2 percent moisture content is best for puffing by a proces thatrapidly heats the flake..The optimum moisture content for any oneparticular flake composition and puffing technique is best determined onan individual basis.

Additional processing steps are utilized if it is so desired. Forinstance a toasting operation is used after the puffing step if it isdesired to change the color of the flake to a more desired rich goldenbrown. Frequently, a slight toasting step also brings out a pleasanttoasted flavor note. i

The flakes can also include various materials to improve taste,appearance and/or functional properties. For instance sugar, salt,flavoring, coloring and/or spices can be used in the formulation eitherin the original dough or as a coating on the puffed flake. Vitamins andminerals can also be included in the formulation to increase thenutritional value of the breakfast food.

The above preferred process has been described in regard to producing aproduct having a flake-type structure. However, if a puffed sphere-typeproduct is desired the above described preferred process only has to bemodified slightly. After the formation of pellettype particles and thetempering period, if any is required, the cereal particles are sentdirectly to the puffing operation, by-passing the flaking roll or rolls.Thus, the only modification in the process described for producing aflake product is the omission of passing the pellet-like particlesthrough the flaking step.

ln accordance with another and preferred aspect of the presentinvention, a cereal grain selected from the group consisting of corn,wheat, rice, barley, oats, and mixtures thereof, is admixed with thepartially hydrolyzed soy protein and thereafter processed to form acomposite final product that still has a high protein content, i.e.,greater than percent. As with the cereal product made from soy prteinalone forming the structure of the product, the cereal productcomprising treated soy protein and a cereal grain is produced by generalprocesses of cereal manufacture depending on the desired form, type, orcondition of the final prod- UCt.

In the preferred process the additive cereal grain is separately cookedor gelatinized and then mixed with the partially hydrolyzed soy proteinto form a dough. This dough is then processed in accord with thepreferred process above described with respect to the all soy proteincereal product. That is, the dough is extruded, pelletized, dried ifnecessary, and puffed. Alternatively, the pellets are flaked prior tothe puffing operation to form a flaked product. Toasting and/or acoating operation may be added to the process.

The cooking or gelatinizing of the cereal additive is performed underconditions similar to those commonly used in the industry. Thus, eithera batch cooking or continuous cooking operation is used. Differentmethods of cooking include heating at atmospheric pressure in anagitated kettle, heating at elevated pressure in a tumbling type mixerand heating under high pressure in a continuous mixer-extruder.

The amount of water and temperature needed to gelatinize the grainsdepends upon the particular grain and the particular method used. Thepreferred method of gelatinizing the cereal grain is by cooking in anextruder under pressure. Such a process is continuous and can beaccomplished with greater ease. Additionally, the use of higer pressuresattainable in the extruder allow the use of higher temperatures and alsolower water levels than possible with a batch type cooking operation.The use of lower water levels thus minimizes the amount of dryingrequired in subsequent steps. Using an extrusion type process at 100psig to 200 psig pressure and temperatures in the range of 250F to 350F,12 to percent water based on the total mixture is sufficient togelatinizc the cereal grain.

The gelatinized cereal grain can, at this point, be added to thepreviously partially hydrolyzed soy protein and further processed toproduce the cold cereal product. Preferably, though, the water contentof the gelatinized cereal grain is reduced prior to mixing with thepartially hydrolyzed protein source. This additional operation ispreferred at this point in the process so that subsequent handling andprocessing operations proceed more smoothly. Excessive moisture levelsin the mixture cause subsequently formed individual cereal forms orshapes to lack body or be overly soft and difficult to handle. Theamount of moisture present in the cooked cereal grain at the time ofaddition to the treated soy protein mixture must be relatively lowbecause water still present from the partial hydrolysis of soy proteinwill contribute significantly to the total moisture content of themixture. It is preferred that 15 to 30 percent water be present in thesoy proteincooked grain mixture when the product is being made by thepreferred method. Accordingly, to reach the lower water levels oftendesired, less than 5 percent water must be present in the cooked cerealgrain prior to mixing with the soy flour. If the cereal is gelatinizedby the continous extrusion method under pressure, as in the preferredcooking method, the resultant extrudant may flash dry and thereaftercontain less than 5 percent water and as such would not need theadditional drying operation.

Depending on the cooking process used, it may be necessary to firstbreak any lumps of cooked cereal formed during the cooking process sothat proper drying, if needed, can be performed. Some cereals, inparticular corn, have a tendency to agglomerate during the cooking stageand as a result the lumps are more difficult to dry thoroughly. Anyconventional lump-breaker is satisfactory for aiding in making thecooked cereal more susceptible to a thorough drying. If, of course, nolumps or agglomerates were formed or drying is not needed, thisoperation is eliminated. Various types of equipment are available forthe lump-breaking operation and are used with equivalent results.

The cooked cereal grain can now be combined with the partiallyhydrolyzed soy protein or, optionally, given one more treatment toimprove its processability. That is, the cooked cereal grain can bevigorously milled to increase its free starch content. In this regardreference is made to commonly assigned copending application Ser. No.76990, Production of Puffed Readyto-Eat Cereal Products, by William T.Bedenk and John W. Mitchell.

The cooked cereal grain is now combined with the partially hydrolyzedsoy protein to form a dough and thereafter processed in the mannerheretofore described with respect to the treated soy protein alone.Corn, rice, oats, and wheat all contain relatively low protein contentsthat must be accounted for when determining the total protein content ofa soy flour-cereal grain cereal product. The approximate proteincontents of corn, rice, oats, and wheat are 9 percent, 7 percent, l4percent, and 12 percent, respectively. The exact protein content of acereal grain and of the soy protein are determined by methods well knownto those skilled in the art. The partially hydrolyzed soy protein andgelatinized cereal grain are combined together in proportions such thatthe end product has a protein content of at least 20 percent.

I It should be understood that the soy protein partially hydrolyzed astaught herein can be further processed into a ready-to-eat breakfastcereal by processes in addition to the previously described extruding,pelletizing, flaking, and/or puffing process. For instance, oneespecially preferred method is the extrusion puffing method. In thismethod the partially hydrolyzed soy protein is mixed with otheringredients that go to making up the desired cold cereal composition,e.g., sugar, salt, gelatinized cereal grain, and thereafter fed into anextruder-puffer. Under operating conditions of 500 psig-] ,000 psig atthe puffing end, temperatures of 280 to 320F and a speed of rotation ofthe extruder screw of 120-300 rpm, a very satisfactory puffed coldcereal product is obtained.

The following examples are given for the purpose of illustrating theproduction of the novel cold cereal products. Unless otherwiseindicated, all percentages given are on a weight basis.

EXAMPLE 1 Formulation:

Soy isolate 662 grams Water 830 grams Papain 0.16 grams (242 ppm)Alcalase 0.08 grams (121 ppm) The above ingredients are mixed and heldat 100F for 1 hour. To 1,350 grams of this mixture is added 1,250 gramsof gelatinized corn grits. The resultant blend is then passed through anextruder at a temperature of 200F. The extrudant is in the form ofstrands having a diameter of about 3/16 inch. These strands are slicedto form pellet shapes 3/16 inch in length. The pellets are passedthrough a 2-roll mill to form flakes of about 1 1 mil thickness. Theseflakes are now puffed in a salt puffer wherein the salt is maintained atabout 330F. After toasting the puffed flakes at 400F for 0.8 minutes theresultant cold cereal product is tested by an expert food panel.

The cold cereal product is tested for tenderness as measured on a -10scale with a rating being the most tender rating. The product is testedat 0 minutes and at intervals of 2, 4, 6, and 8 minutes after beingwetted with milk. The results are as follows:

Time 0 2 4 6 Tenderness 6.25 6.5 8.0 9.0

COMPARATIVE TEST A A cold cereal product is made by the same formulationand process steps and conditions of Example 1 with the exception that0.24 papain (363 ppm) is sub stituted for the papain-alcalase mixtureabove.- The same panel tested the resultant product in the same manneras Example I and rated it as follows:

Time 0 6 COMPARATIVE TEST B A cold cereal product is made by the sameformulation and process steps and conditions of Example I with theexception that 0.32 grams papain (484 ppm) is substituted for thepapain-alcalase mixture. The same panel rated the resultant product onthe basis of the above described test as follows:

Time

0 2 4 Tenderness 5.75 6.25 6.75 8.5 9

A comparison of the ratings of the product of Comparative Test B and theproduct of Comparative Test A shows that even though a greater level ofpapain (33 percent greater) is used, the resultant product is verysimilar in regard to tenderness.

A comparison of the ratings of the product of Comparative Test B withthe ratings of the product of Example 1 shows that even an increasedlevel of a single proteolytic enzyme (484 ppm for this comparative testvs. a total enzyme level of 363 ppm for Example 1) does not give astender a product as does a papain and other proteolytic enzyme mixture.Since enzyme level affects the degree of partial hydrolysis, it can beseen that a substantially greater level of a single proteolytic enzymewould be needed to give the same degree of partial hydrolysis and hencesame tenderness rating as obtained by the specific mixtures of thisinvention.

What is claimed is:

1. In a process for the production of a ready-to-eat breakfast cerealcontaining soy protein and having a protein content of at least 20percent, said process including the steps of preparing a soy proteincontaining cereal dough, shaping said dough, and puffing said dough, theimprovement which comprises: reacting the soy protein with water forabout 1 minute to about 120 minutes at about F to about 160F in thepresence of from about 15 ppm to about 2,500 ppin of papain and fromabout 5 ppm to about 2,500 ppm of at least one other proteolytic enzyme,thereby causing partial hydrolysis of the soy protein to a degree thatresults in a product which is easily processed and which has anacceptable taste.

2. The process of claim 1 wherein the proteolytic enzyme is selectedfrom the group consisting of pepsin, bromelin, ficin, alcalase,maxitase, thermoase, pronase, and mixtures thereof.

3. The process of claim 1 wherein the soy protein is selected from thegroup consisting of soy flour, soy protein concentrate, and soy proteinisolate.

4. A process for making a palatable ready-to-eat breakfast cereal havinga protein content of at least 20 percent comprising:

a. reacting soy protein with water in the presence of from about 15 ppmto about 2,500 ppm of papain and from about 5 ppm to about 2,500 ppm ofat least one other proteolytic enzyme for 1 minute to minutes at 80F toF, thereby causing a partial hydrolysis of the soy protein;

b. extruding the partially hydrolyzed soy protein into strands of adesired shape;

c. slicing the strands into pellet-like particles; and

d. pufflng the pellet-like particles to form the readyto-eat breakfastcereal.

5. The process of claim 4 further comprising blending a gelatinizedcereal grain with the partially hydrolyzed soy protein prior to theextruding step.

6. The process of claim 5 wherein the proteolytic enzyme is selectedfrom the group consisting of pepsin, bromelin, ficin, alcalase,maxitase, thermoase, pronase, and mixtures thereof.

7. The process of claim 6 wherein the gelatinized cereal grain is corn.

8. The process of claim 7 further comprising flaking the pellet-likeparticles prior to puffing.

9. The process of claim 4 wherein the papain and at least one otherproteolytic enzyme are each present in an amount ranging from 100 ppm to300 ppm by weight of the soy protein.

10. The process of claim 9 wherein the soy protein is reacted with thewater at 120F to 130F for 1 minute to 5 minutes.

11. A process for making a palatable ready-to-eat breakfast cerealhaving a protein content of at least 20 percent comprising:

a. reacting soy protein with water in the presence of from about ppm toabout 2500 ppm of papain and from about 5 ppm to about 2500 ppm ofanother proteolytic enzyme for 1 minute to 120 min utes at 80F to 160F,thereby causing a partial hydrolysis of the soy protein; and

b. extruding-puffing the partially hydrolyzed soy protein to form theready-to-eat breakfast cereal.

12. The process of claim 11 wherein l5 ppm-2500 ppm of the papain and 5ppm-2500 ppm of at least one other proteolytic enzyme by weight of thesoy protein are present in the reaction.

13. The process of claim 11 wherein the partially hydrolyzed soy proteinis extruded-puffed under a pressure of 500 psig 1000 psig and atemperature of 280F 320F.

14. The process of claim 13 further comprising blending a gelatinizedcereal grain with the partially hydrolyzed soy protein prior to theextruding-puffing step.

15. The process of claim 14 wherein the proteolytic enzyme is selectedfrom the group consisting of pepsin, bromelin, ficin, alcalase,maxitase, thermoase, pronase, and mixtures thereof.

16. The process of claim 15 wherein the gelatinized cereal grain is com.

2. The process of claim 1 wherein the proteolytic enzyme is selectedfrom the group consisting of pepsin, bromelin, ficin, alcalase,maxitase, thermoase, pronase, and mixtures thereof.
 3. The process ofclaim 1 wherein the soy protein is selected from the group consisting ofsoy flour, soy protein concentrate, and soy protein isolate.
 4. Aprocess for making a palatable ready-to-eat breakfast cereal having aprotein content of at least 20 percent comprising: a. reacting soyprotein with water in the presence of from about 15 ppm to about 2,500ppm of papain and from about 5 ppm to about 2,500 ppm of at least oneother proteolytic enzyme for 1 minute to 120 minutes at 80*F to 160*F,thereby causing a partial hydrolysis of the soy protein; b. extrudingthe partially hydrolyzed soy protein into strands of a desired shape; c.slicing the strands into pellet-like particles; and d. puffing thepellet-like particles to form the ready-to-eat breakfast cereal.
 5. Theprocess of claim 4 further comprising blending a gelatinized cerealgrain with the partially hydrolyzed soy protein prior to the extrudingstep.
 6. The process of claim 5 wHerein the proteolytic enzyme isselected from the group consisting of pepsin, bromelin, ficin, alcalase,maxitase, thermoase, pronase, and mixtures thereof.
 7. The process ofclaim 6 wherein the gelatinized cereal grain is corn.
 8. The process ofclaim 7 further comprising flaking the pellet-like particles prior topuffing.
 9. The process of claim 4 wherein the papain and at least oneother proteolytic enzyme are each present in an amount ranging from 100ppm to 300 ppm by weight of the soy protein.
 10. The process of claim 9wherein the soy protein is reacted with the water at 120*F to 130*F for1 minute to 5 minutes.
 11. A process for making a palatable ready-to-eatbreakfast cereal having a protein content of at least 20 percentcomprising: a. reacting soy protein with water in the presence of fromabout 15 ppm to about 2500 ppm of papain and from about 5 ppm to about2500 ppm of another proteolytic enzyme for 1 minute to 120 minutes at80*F to 160*F, thereby causing a partial hydrolysis of the soy protein;and b. extruding-puffing the partially hydrolyzed soy protein to formthe ready-to-eat breakfast cereal.
 12. The process of claim 11 wherein15 ppm-2500 ppm of the papain and 5 ppm-2500 ppm of at least one otherproteolytic enzyme by weight of the soy protein are present in thereaction.
 13. The process of claim 11 wherein the partially hydrolyzedsoy protein is extruded-puffed under a pressure of 500 psig - 1000 psigand a temperature of 280*F - 320*F.
 14. The process of claim 13 furthercomprising blending a gelatinized cereal grain with the partiallyhydrolyzed soy protein prior to the extruding-puffing step.
 15. Theprocess of claim 14 wherein the proteolytic enzyme is selected from thegroup consisting of pepsin, bromelin, ficin, alcalase, maxitase,thermoase, pronase, and mixtures thereof.
 16. The process of claim 15wherein the gelatinized cereal grain is corn.